curl --request GET \
  --url https://eu-gcp-api.vg-stuff.com/v3/variables/{variableId} \
  --header 'Authorization: Bearer <token>'

{
  "success": true,
  "message": "<string>",
  "data": {
    "id": "<string>",
    "in": "<string>",
    "type": "string",
    "value": "<any>",
    "defaultValue": "<any>",
    "key": "<string>",
    "description": "<string>",
    "required": true,
    "reusable": true,
    "isEnv": true,
    "isSystem": true,
    "isGlobal": true,
    "agentId": "<string>",
    "userId": "<string>"
  }
}